1. Field of the Invention
The present invention relates to processing equipment for casting articles and particularly to centrifugal casting apparatus. Most advantageously the invention can be used in machine building and some other branches of industry for centrifugal casting of articles from ferrous and non-ferrous metals and also from glass, plastics, and ceramics.
2. Description of the Prior Art
Though the centrifugal casting has been known and widely used for a long period of time, there still exist difficulties relating to filling the mould with a melt and proportioning the same. The fact that a great number of patents concerning improvements in centrifugal casting apparatus have been recently granted to inventors in various countries shows that this problem is very urgent at present. Even now in some enterprises, molds are manually filled with a melt by pouring it from above with the aid of a dipper serving as a batch meter. The above procedure makes it possible to accurately measure out the batches of the melt without any special equipment and to rule out the formation of crusts on the outer surface of the mould. However, this same procedure fails to provide for a high efficiency of the production process and is very labor-consuming.
Known in the art are apparatus which allow proportioning the melt and filling the molds therewith to be mechanized and, to some extent, automatized. In particular, there is known a centrifugal casting apparatus comprising a mold mounted for rotation about its vertical axis and having a bottom provided with an axial sprue channel (see French Pat. No. 1,587,187, Int. Cl..sup.2 B 22 D 13/00). In direct communication with the sprue channel is a siphon tubing extending therefrom into the melt contained in a crucible. The melt is delivered into the mold through the siphon tubing by an electromagnetic pump or a vacuum pump.
The mold being filled with the melt, a casting starts to solidify around its periphery and at the same time is fed with the portion of the melt contained in the siphon tubing. Owing to the large diameter of the siphon tubing and the presence of a heat insulating material, this portion of the melt solidified last to form a shrinkage head. It is clear that this shrinkage head is to be removed to obtain a finished product, which removal involves additional expenditures and irretrievable losses of the process raw material. In addition, electromagnetic pumps are unusable for casting plastics, glass, and ceramics, while vacuum pumps are inefficient for casting high density materials.
Known in the art is also a centrifugal casting apparatus wherein a melt is delivered into a mold by centrifugal forces, as described in USSR Inventor's Certificate No. 520,181, Int. Cl..sup.2 B 22 D 13/10. This apparatus comprises a mold mounted for rotation about the vertical axis thereof and having a bottom provided with a through axial opening. At the opening in the bottom there is disposed a means adapted to be partially immersed into the melt for feeding the latter into the mold. This means is made in the form of a collect secured to the bottom of the mold and having an upwardly extending channel. The mold and collet are connected with a rotation drive and a vertical motion drive. By lowering the mold being rotated the collet is immersed into the melt which, under the action of centrifugal forces, ascends through the channel in the collet and fills the mould. Then the assembly of the mold and collet is raised; as this takes place, the major part of the melt pours down from the collet into the dispensing crucible. However a part of the melt inevitably remains in the collet, which impairs the accuracy of the proportioning and leads to the formation of a shrinkage head. It will be understood that the removal of the shrinkage head involves additional expenditures and irretrievable losses of the process raw material. In addition, the above apparatus suffers from another drawback which consists in that slag inevitably gets into the mold thereby adversely affecting the quality of the castings.